Warnings fixed for test_ssim.py (#2360)

* first commit

* changing channel_axis to -1 for multichannel argument

* deprecate permute(0,2,3,1)  instead use channel_axis=1 that is (B,C,H,W)

Co-authored-by: Sylvain Desroziers <sylvain.desroziers@gmail.com>
Co-authored-by: vfdev <vfdev.5@gmail.com>

Author: 3 people

tests/ignite/metrics/test_ssim.py

@@ -74,14 +74,14 @@ def _test_ssim(y_pred, y, data_range, kernel_size, sigma, gaussian, use_sample_c
     ssim.update((y_pred, y))
     ignite_ssim = ssim.compute()
 
-    skimg_pred = y_pred.permute(0, 2, 3, 1).cpu().numpy()
+    skimg_pred = y_pred.cpu().numpy()
     skimg_y = skimg_pred * 0.8
     skimg_ssim = ski_ssim(
         skimg_pred,
         skimg_y,
         win_size=kernel_size,
         sigma=sigma,
-        multichannel=True,
+        channel_axis=1,
         gaussian_weights=gaussian,
         data_range=data_range,
         use_sample_covariance=use_sample_covariance,
@@ -135,14 +135,14 @@ def update(engine, i):
         assert "ssim" in engine.state.metrics
         res = engine.state.metrics["ssim"]
 
-        np_pred = y_pred.permute(0, 2, 3, 1).cpu().numpy()
+        np_pred = y_pred.cpu().numpy()
         np_true = np_pred * 0.65
         true_res = ski_ssim(
             np_pred,
             np_true,
             win_size=11,
             sigma=1.5,
-            multichannel=True,
+            channel_axis=1,
             gaussian_weights=True,
             data_range=1.0,
             use_sample_covariance=False,
@@ -159,9 +159,9 @@ def update(engine, i):
         assert "ssim" in engine.state.metrics
         res = engine.state.metrics["ssim"]
 
-        np_pred = y_pred.permute(0, 2, 3, 1).cpu().numpy()
+        np_pred = y_pred.cpu().numpy()
         np_true = np_pred * 0.65
-        true_res = ski_ssim(np_pred, np_true, win_size=7, multichannel=True, gaussian_weights=False, data_range=1.0)
+        true_res = ski_ssim(np_pred, np_true, win_size=7, channel_axis=1, gaussian_weights=False, data_range=1.0)
 
         assert pytest.approx(res, abs=tol) == true_res